In a country such as India, with its vast population and inequalities in access to appropriate healthcare and amenities such as safe water, universal availability of vaccines has the potential to save lives and reduce childhood mortality and morbidity.

The Expanded Programme of Immunization in 1978 that provided primary vaccination against tuberculosis, diphtheria, pertussis, tetanus and typhoid was rechristened the Universal Immunization Programme (UIP) in 1985 with the addition of single-dose measles vaccine. No new vaccine was added to the programme for the next 16 years until the partial introduction of hepatitis B vaccine in 2002–2003. The past decade, however, has seen a much-needed increase in government-provided vaccines against several major killers of children, with the introduction of Japanese encephalitis (JE) vaccine in JE endemic districts from 2006 and the second dose of measles vaccine in 2010, scaling up of hepatitis B vaccination and introduction of Haemophilus influenzae type b (Hib) vaccine in 2011,[1] followed by introduction of inactivated polio vaccine in 2015 and rotavirus vaccine in 2016.

With almost 27 million children born each year, India accounts for one-fifth of child deaths worldwide. Although child deaths have halved since 1990[2] and the last case of wild poliovirus was reported in 2011,[1] India continues to have a significant proportion of under-immunised children. The Government of India's Mission Indradhanush, launched in December 2014 with the aim of improving and sustaining vaccine coverage to over 90% by 2020, has provided vaccines to 75.5 lakh children and 26.8 lakh pregnant women with the elimination of maternal and neonatal tetanus in 2015.[3]

The latest addition to the UIP is the measles-rubella (MR) vaccine slated for introduction in five states and union territories (Karnataka, Tamil Nadu, Pondicherry, Goa and Lakshadweep) in February 2017,[4] to be given to all children aged 9 months to 15 years before replacing measles vaccine administered in the immunisation schedule at 9–12 months and 16–23 months of age.

Measles has always been one of the more difficult diseases to control, from a public health perspective. It has the highest attack rate amongst vaccine-preventable diseases and is the single most common vaccine-preventable cause of death in children in India.[5] Mathematical modelling has estimated that the herd immunity required for interrupting wild virus measles transmission ranges from 94% to 98%.[6] Data from the National Family Health Survey indicate that measles vaccine coverage in children aged 12–23 months, although improved from the 58.8% documented in 2005–2006, is still <90% in most states in 2015–2016.[7] Inadequate vaccine coverage and the susceptibility of infants to wild measles virus in the community have prevented India from increasing the age of first dose of measles vaccine from 9 months to 1 year, with the disadvantage of lower seroprotection at the 9-month mark (80%–94%) compared to the over 95% seroprotection expected if given at or after 1 year of age.[8],[9] Added to this is the fact that studies outside Asia have suggested that initial immunisation at less than a year of age has a negative impact on antibody levels attained after a second dose of the vaccine.[10],[11],[12] All these factors probably contribute to the low measles vaccine efficacy documented in India that ranges from 66% to 84%.[13] This in turn has led to several outbreaks of measles in India [13],[14],[15] that often involve children younger than the recommended age for vaccination,[14] especially in areas with low vaccine coverage even within states with high overall coverage figures.

Rubella, although a more subclinical disease with less severe manifestations in those infected, leads to devastating consequences in the form of congenital rubella syndrome (CRS) in infants born to mothers infected with rubella, especially in the first trimester. The absence of a nationwide reporting system for CRS and lack of uniform testing have led to inadequate data on the population-based burden of disease. About 10%–15% of intrauterine infections are thought to be due to rubella, with various studies implicating CRS as the cause in 1%–60% of ocular abnormalities, 1.5%–29% of congenital deafness and about 30% of congenital heart disease.[16] Although there are no national estimates of women of childbearing age at risk, various serosurveys have documented susceptibility to rubella in significant proportions of young women. A study in Jammu on 11–18-year-old school girls showed that 33% lacked evidence of seroprotection against rubella.[17] Amongst 18–24 years old college students, seronegativity to rubella ranged from 12% in Mumbai [18] to 34% in girls in Pune.[19] Another serosurvey of medical and nursing students at Manipal University showed that 16.6% were susceptible to rubella, with 10.5% of those previously vaccinated having inadequate antibody levels.[20] Similar to measles, waning of antibodies against rubella has been documented in those vaccinated at younger ages,[21] and outbreaks of rubella are well documented,[15] emphasising the need for renewed opportunities for vaccination in older children and adolescents. A survey on employees at three eye hospitals in Tamil Nadu showed susceptibility to rubella ranging from 12% to 21%, with the highest proportion of susceptibles documented amongst married women.[22] Data from the National Institute of Communicable Diseases showed 12% overall susceptibility to rubella amongst pregnant women in Delhi from 1988 to 2002[23] while another study documented 31% susceptibility amongst women in Amritsar in 2004.[24] Susceptibility to rubella was also shown to be higher in rural areas, attributed to lower population density, in two studies both of which showed more susceptibility to rubella in women from a higher socioeconomic class.[24],[25] Pregnant women with bad obstetric history were also shown to have evidence of recent infection, with rubella IgM positivity ranging from over 50% in those with intrauterine deaths, stillbirth and premature delivery to 17%–20% in those with abortions and recurrent abortions.[26]

Control of both rubella and measles rests on maintaining high and sustained vaccination coverage. Unlike Hib vaccination where even partial coverage within a community leads to a reduction of disease due to the herd effect,[27] single-dose rubella vaccine in young children combined with low rubella vaccination coverage has been shown to shift the age of incidence of rubella towards adolescents and young adults and lead to outbreaks of CRS.[28] In this context, the Government of India's decision to give MR vaccine to all children from 9 months to 15 years of age will help to prevent the shift of rubella towards adolescents and women of childbearing age. Similarly, measles vaccination coverage has to remain high to reduce the pool of susceptibles in the population who are at risk for acquisition of wild measles virus infection. The Government's strategy for measles control in India has been to use the established field surveillance network and personnel from the successful polio eradication campaign to detect and report measles outbreaks and to administer second doses of measles vaccine, as well as for catch-up vaccination in areas with low vaccine coverage.[29] In addition to immunisation, continued surveillance as well as monitoring and intervention for adverse events and programmatic errors is essential for sustained rubella and measles vaccination coverage over time. Elimination of measles and control of rubella by 2020 will necessitate the rapid provision of MR vaccine to other states in the country, as well as another opportunity in future for older children and adolescents to receive measles- and rubella-containing vaccines in the national programme.